The present invention relates to information reproducing techniques for information recording media. In particular, the present invention relates to an information reproducing technique for an optical disk.
DVDs with a capacity of 4.7 gigabytes and above are becoming common as high density and high capacity optical disks to replace CDs. In addition, the next generation of optical disks using blue lasers is currently being standardized. Recording and reproduction technologies in this field are advancing toward still higher density, and there is a demand for superior signal processing techniques.
Among the signal processing techniques employed for such familiar optical disks as CDs and DVDs, is one referred to as “scramble.” This signal processing is characterized in that the length of data composed of pits, spaces, marks and the like on an optical disk is changed randomly at long intervals. These changes are intended to reduce crosstalk and adverse effects on the servo error signal due to adjacent identical data, to obtain a good data reproduction waveform and a steady tracking servo.
Moreover, in the case of phase-change disks such as CD-RW, DVD-RAM and DVD-RW, writing to the same place a number of times deteriorates the disk material and may result in a situation where data cannot be recorded or reproduced properly. One solution to this problem is a method disclosed in Japanese Patent Laid-open No. 2002-216358. This method superimposes different data on recorded data each time the data is written to change the written data each time.
This invention provides an improved solution in which when recording a disk, scrambling is performed after error correction encoding in the process of data processing.